1. Field of the Invention
The present invention relates to an ophthalmologic image pickup apparatus and a measuring method, and more particularly, to an ophthalmologic image pickup apparatus and a control method therefor for measuring movement of an eye to be inspected by using an image of the eye to be inspected.
2. Description of the Related Art
In recent years, as an apparatus for taking an image of an eye to be inspected, there has often been used an ophthalmologic image pickup apparatus which takes an image of the eye to be inspected by scanning the eye to be inspected with measuring light, such as an optical coherence tomography (OCT) capable of acquiring a three-dimensional image, and a confocal scanning laser opthalmoscope (SLO) for acquiring a high resolution moving image. Such an ophthalmologic image pickup apparatus needs some time from start of taking an image until the end thereof, and hence it is vulnerable to the influence of involuntary eye movement, eye movement due to poor fixation, or eye movement due to face movement. Therefore, it is more important to track the eye movement.
As a method of tracking the eye to be inspected, U.S. Pat. No. 4,856,891 discloses a tracking method involving radiating a rectangular tracking beam to a target blood vessel on the fundus, and detecting reflection light of the tracking beam by two orthogonal lines on a two-dimensional sensor so as to measure two-dimensional movement of the fundus. In addition, U.S. Pat. No. 5,943,115 discloses a tracking technology involving radiating a tracking beam that scans a characteristic portion of the fundus in a circular manner, and measuring two-dimensional movement of the fundus based on a phase of the reflection light. However, in the methods in these documents, an additional optical system for tracking is necessary, and eye rotation cannot be detected. Therefore, Japanese Patent Application Laid-Open No. 2011-56069 discloses a technology in which a template image that is a small area image having a feature is extracted from a fundus observation image, and movement of the fundus is measured by pattern matching of searching for a portion that is most similar to the template image.
Here, the technology disclosed in Japanese Patent Application Laid-Open No. 2011-56069 performs the two-dimensional image processing, and hence it takes time to measure the movement of the eye to be inspected.